A rectangular deflector plate of height 1.5 m and width 4.0 m is mounted vertically in a wind tunnel, as shown in the diagram.
a.[3]
A horizontal stream of air with speed 20 m s-1 blows at right angles to the front face of the plate for 1.5 s. The density of air is 1.2 kg m-3.
Show that the mass of air which hits the plate in this time is 216 kg.
b.[3]
All the air incident on the plate is deflected at 90∘ 90^\circ\,90∘ to its original direction, parallel to the surface of the plate. Calculate the magnitude of the force F F\,F exerted by the air stream on the plate.